#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main()
{
    int a;
    clock_t start =clock();

    srand((unsigned)time(NULL));
    a = rand();
    printf("%d\n", a);

     
    long i=10000000000L;
    while (i--)
    {
        /* code */
    }
     clock_t end =clock();
     printf("程序执行了%.3f s\n",(double)(end-start)/CLOCKS_PER_SEC);
    return 0;
}